Method and apparatus for generating elliptical images on a raster-type video display

Abstract

A method and apparatus provides for the generation of a number of elliptical images on a raster scan video display screen by storing information indicative of a predetermined model image, and for each elliptical image to be displayed, storing data indicative of the vertical and horizontal eccentricity of each image, and its display location. During display time, the vertical eccentricity, horizontal eccentricity, and display location binary information for each elliptical is accessed and used to sequentially read selected portions of the model image information to produce therefrom address signals indicative of the location of individual horizontal display elements that make up the desired elliptical image. The address signals are applied to a random access memory to store marker information indicative of the elliptical image at memory locations corresponding to the position on the display screen that the image will take. The random access memory is sequentially scanned in synchronism with the scan of the electron beam used to form the raster, converted to video information and displayed.

I claim: 
     
       1. Apparatus for forming a movable elliptical image on a video display screen of the type having a scanning electron beam forming a plurality of horizontal scan lines in response to timing signals including vertical and horizontal retrace intervals, said image being variable in eccentricity, the apparatus comprising: first memory means for containing binary data indicative of a plurality of horizontal elements of a model image;   second memory means for storing a data word group descriptive of at least the eccentricity and display screen location of said elliptical image;   first combining means coupled to said second memory means and resposive to at least a portion of said data word group for forming first address signals and for applying said address signals to said first memory means to access therefrom said binary data indicative of selected ones of said horizontal elements of said model image for each horizontal scan line used to form said elliptical image;   second combining means coupled to said first and second memory means and responsive to a remaining portion of said data word group and said accessed binary data to form therefrom second address signals indicative of the location of said horizontal elements on said display screen;   random access memory means coupled to said second combining means and responsive to said second address signals for storing marker information at memory locations corresponding to positions on the display screen; and   means accessing said random access memory means in synchronism with said scanning electron beam.   
     
     
       2. Apparatus for forming a movable elliptical image on a video display of the type having an image-forming beam for forming a plurality of horizontal lines in response to timing signals, including horizontal retrace intervals, said elliptical image being variable in eccentricity and formed from a number of horizontal display elements, the apparatus comprising: first memory means for containing binary data indicative of a model image;   second memory means for storing a data word group indicative of said eccentricity of said elliptical image;   accessing means coupled to said first and second memory means and responsive to a first portion of said data word group for sequentially forming and applying first address signals to said first memory means to read therefrom said binary data;   combining means coupled to said first and second memory means for combining a second portion of said data word with said accessed binary data to form therefrom second address signals indicative of said elliptical image horizontal display elements;   random access memory means responsive to said second address signals for storing marker information for each horizontal display element at memory locations corresponding to locations on said video display; and   means for sequentially reading said random access memory means in synchronism with said image-forming beam to obtain said marker information, and for forming therefrom video signals indicative of said elliptical image.   
     
     
       3. The apparatus of claim 2, said first portion of said data word group including a memory address word and a vertical eccentricity word, said accessing means including means for adding said first memory address word and said vertical eccentricity word to form first address signals. 
     
     
       4. The apparatus of claim 2, said first portion of said data word group including memory address word and a vertical eccentricity word, said eccessing means including means for producing a number of sequential accumulations from said memory address word and said vertical eccentricity word, said first address signals being formed from a portion of each of said accumulations. 
     
     
       5. The apparatus of claim 2, the second portion of said data word including a horizontal eccentricity data word, the combining means including means for multiplying said accessed binary data by said horizontal eccentricity word to produce a result from which is formed said second signals. 
     
     
       6. The apparatus of claim 5, the second portion of said data word group including a position data word indicative of the relative location of said elliptical image on said display screen, said combining means including means for summing said position data word and said result to form said second signals. 
     
     
       7. Apparatus for forming a plurality of elliptical images on a video display screen of the type having an image-forming beam for forming a plurality of horizontal scan lines in response to timing signals, including horizontal retrace intervals, said elliptical images each being variable in size and formed from a number of horizontal display elements, the apparatus comprising: first memory means for containing a model image in the form of binary information indicative of a plurality of predetermined horizontal display elements;   second memory means for storing for each elliptical image data indicative of said size;   first accessing means responsive to a first portion of said data for each elliptical image for forming first address signals during each horizontal retrace interval and for applying said first address signals to said first memory means to read therefrom binary information indicative of one of said predetermined horizontal display elements;   combining means for receiving and combining said accessed binary information with a second portion of said data to produce therefrom second address signals;   random access memory means responsive to said second address signals for storing marker information indicative of the horizontal display elements at memory locations corresponding to positions at which the horizontal display elements are to be displayed; and   second accessing means for sequentially accessing said random access memory means in synchronism with said image-forming beam.   
     
     
       8. The apparatus of claim 7, wherein said elliptical images are individually positionable on said video display screen. 
     
     
       9. The apparatus of claim 8, said plurality of elliptical images being arranged to simulate a twisting, turning tunnel, each larger elliptical image forming a window containing smaller elliptical images, said random access memory means including priority-determining means for inhibiting marker information being stored for elliptical images or portions thereof outside said window presented by larger elliptical images. 
     
     
       10. The apparatus of claim 7, said data word group including color information, and including means responsive to said second accessing means for accessing said color information in synchronism with said image-forming beam. 
     
     
       11. Apparatus for generating video signals used for displaying an elliptical image that is variable in size, shape and position on a video display screen comprising: first means for storing information indicative of a model image of predetermined size and shape;   second means for storing data indicative of the size, shape, and display screen location of the elliptical image;   
     
     
       third means for accessing said first and second means and for combining said predetermined model image information and said data to provide binary signals indicative of the location on the display screen of a plurality of display points indicative of the periphery of said elliptical image; random access memory means responsive to said binary signals for storing markers at location corresponding to positions on said display screen of said periphery; and   means for sequentially reading said markers from said random access memory means and for forming therefrom said video signals.   
     
     
       12. A method for generating an elliptical image on a video display screen of the type having an image forming beam scanning said display to form a plurality of horizontal lines, said elliptical image being variable in eccentricity and formed from a number of horizontal display elements, the method comprising the steps of: storing binary data indicative of a model image;   storing a data word group indicative of said eccentricity of said elliptical image;   accessing said data word group and utilizing a first portion thereof to form a number of first address signals;   sequentially using said first address signals to access said binary data;   combining said accessed binary data with a second portion of said data word group to provide second address signals indicative of said elliptical image horizontal display elements;   storing marker information for each horizontal display element at memory locations designated by said second address signals and corresponding to locations on said video display screen; and   sequentially reading said random access memory means in synchronism with said image forming beam to obtain said marker information and for forming therefrom video signals indicative of said elliptical image.